can she do this?

I currently am living with my son in a one bedroom apt since dec 1. i moved him out of the residence where me and my girlfriend were living. she is stripping and posting ads on craigslist for topless masseuse. we both filed for custody of my son on dec 5 and was given a court date of next year dec 2014. i recently filed for expedited hearing which is set for mar 21 2014. i just recieved court papers from my ex for child support of my son. i'm a little confused how she can file for support of my son, if he's been living with me and i pay everything for him with no help from her. she has seen him once since dec 1 it was on dec 27th and its now jan 8 he's talked to her 3 times on the phone. the house were she lives when we left had no heat and the water and elecrtic were cut on illegally without my knowledge. she is recieving food stamps for a son she has seen once in almost two months. she has another daughter as well who from what i hear isn't living at the home with her either.